Scattering Properties of the Dust in the Reflection Nebula IC 435
Gordon, Karl D.; Calzetti, Daniela; Bianchi, Luciana; Bohlin, Ralph C.; Witt, Adolf N.
Abstract
New lUE observations of the reflection nebula IC 435 are presented, and the scattering properties of the nebular dust grains are derived. Previous studies of this nebula suggested the presence of enhanced scattering in the 2175 Å interstellar extinction bump, which the new data do not confirm. The UV observations plus optical data from the literature determine the most likely star-nebula geometry, the nebular dust density distribution, and the values of the albedo and the phase function asymmetry for the dust grains. The results show a broad minimum for the albedo around 2300 Å followed by rising values in the far-UV, up to α ≃ 0.75-0.8. The phase function for the nebular grains tends to be forward-scattering in the UV, with values for the phase function asymmetry rising from g ≃ 0.60 at 3000 Å to g ≃ 0.75 around 1500 Å.